Ink-jet printing apparatus and recovery processing method of ejection port

This application is based on Patent application Ser. No. 2000-89654 filed Mar. 28, 2000 in Japan, the content of which is incorporated hereinto by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ink-jet printing apparatus, and a recovery processing method of an ejection port. More particularly, the invention relates to an ink-jet printing apparatus and a recovery processing method of an ejection port having a function for recovering or maintaining good ink ejection performance of a printing head.

2. Description of the Related Art

Associated with the proliferation of information processing equipment, printing apparatuses as peripheral equipment have also proliferated. Particularly, an ink-jet printing apparatus,which performs printing by ejecting ink droplets from a plurality of ejection openings provided in a printing head toward a printing medium, has rapidly proliferated because color printing can be performed easily. Furthermore, associated with a demand for down-sizing, there has been proposed a serial type ink-jet printing apparatus, which alternately repeats a printing operation of moving the printing head in a predetermined direction and ejecting ink droplets during movement of the printing head and a paper feeding operation for feeding the printing medium by a predetermined amount in a direction perpendicular to the motion direction of the printing head.

In such ink-jet printing apparatus, the printing head is frequently mounted on a carriage which can scan in a predetermined direction. In a case of full-color printing, each of the printing heads for respective colors of yellow, magenta, cyan and black is constructed by integrating an ejection opening array and an ink tank. Also, among the printing heads, there are some printing heads, in which only the ink tank is detachable.

On the other hand, as a color image can be easily processed by information processing equipment, there has been an increasing demand for an ink-jet printing apparatus that can readily print those images in full-color printing, with enhanced image quality. To meet the demand, there has been proposed an ink-jet printing apparatus in which high image quality is realized by printing multi-gradation levels of density using the following method.

For example, concerning magenta and cyan, two kinds of inks having mutually different densities, namely, high density ink and low density ink, are provided for dividing ink densities of image data into a greater number of gradation levels for performing printing with such high and low density inks. In the alternative, by switching the ink ejection amount to be ejected from the printing head using only one kind of ink for each color, depending upon the density of the image data, to perform printing with different sizes of dots on the printing medium can realize high gradation levels and high image quality.

Particularly, the method for increasing gradation levels by forming different sizes of dots on the printing medium by switching ink ejection amounts can restrict the number of ink tanks to be loaded. Therefore, such method is effective for down-sizing of ink tanks and down-sizing of the ink-jet printing apparatus.

The printing head switching the ink ejection amount has been disclosed in Japanese Patent Application Laid-open No. 9-254413(1997) and Japanese Patent Application Laid-Open No. 9-48125(1997). In the above-identified publications, it has been proposed to differentiate ejection amounts by arranging a plurality of rows of ejection openings on an ink ejection face and differentiating sizes of ejection openings per row of the ejection openings.

By performing a printing operation many times or by leaving the printing head inoperative for a long period, it is possible to cause variations in ejection amount and/or ejecting direction from the printing head nozzles due to deposition of dust and dirt around the ejection opening or plugging with ink of increased density. In the alternative, ink may be dried to make ejection unstable upon initiation of printing.

In order to prevent drying of ink or ejection failure, the ink-jet printing apparatus is provided with a cap for covering the ejection opening face while the printing head is not used, or is provided with means for performing preparatory ejection at a predetermined position out of the printing region. For example, in an ink-jet printing apparatus disclosed in Japanese Patent Application Laid-open No. 10-100451(1998), a cap covering a plurality of ejection openings is provided.

On the other hand, in the case of the printing head, in which only the ink tank is detachable, when the old ink tank is removed, air may penetrate into an ink passage connecting the ink tank and the ejection opening, or air may penetrate around the ejection opening. Therefore, when the ink tank is exchanged with new ink tank, re-filling of the ink becomes necessary up to around the ejection opening. Therefore, upon exchanging the ink tank, the ejection opening face is covered with the cap to perform suction of the ink by a suction means with driving a pump.

Such recovery operation by the preparatory ejection means, suction means and so on are performed during a printing operation or a non-printing operation, or upon exchanging of the ink tank or the like.

FIGS. 8A and 8B are sections showing a printing head portion and recovery unit portion of the conventional ink-jet printing apparatus.

As shown in FIG. 8A, a printing head <b>83</b> is mounted on a head carriage frame <b>83</b><i>a </i>movably arranged on a pair of upper and lower guide members <b>82</b>. The printing head <b>83</b> is provided with two ejection opening portions <b>83</b><i>b </i>and <b>83</b><i>c </i>projecting downwardly from the lower surface of the head carriage frame <b>83</b>a, namely from a surface opposing the printing medium feeding passage, a black ink tank <b>83</b><i>d </i>and a color ink tank <b>83</b><i>e </i>arranged detachably on the head carriage frame <b>83</b><i>a. </i>

The ejection opening portions <b>83</b><i>b </i>and <b>83</b><i>c </i>are formed with a plurality of ejection openings, respectively. The ejection opening portion <b>83</b><i>b </i>ejects black ink supplied from the black ink tank <b>83</b><i>d </i>and the ejection opening portion <b>83</b><i>c </i>ejects three kinds of inks of cyan, magenta and yellow supplied from the color ink tank <b>83</b><i>e. </i>

It should be noted that the black ink ejection openings <b>83</b><i>f</i>, the yellow ink ejection openings <b>83</b><i>g</i>, the magenta ink ejection openings <b>83</b><i>h </i>and the cyan ink ejection openings <b>83</b><i>f </i>are provided in plural. However, for the purpose of illustration, only one ejection opening is illustrated.

The ink-jet printing apparatus feeds a printing medium by means of a not shown printing medium feeding member, reciprocally scans the printing head and ejects ink droplets from respective ejection openings to form a desired image on the printing medium.

As shown in FIG. 8B, a recovery unit <b>810</b> for providing recovery process for the printing head <b>83</b> is provided. To the recovery unit <b>810</b>, caps <b>89</b><i>b </i>and <b>89</b><i>c </i>for covering the ejection openings <b>83</b><i>b </i>and <b>83</b><i>c </i>are provided. The caps <b>89</b><i>b </i>and <b>89</b><i>c </i>are connected to not shown pumps. The recovery unit <b>810</b> moves up and down to cover the ejection openings <b>83</b><i>b </i>and <b>83</b><i>c </i>with the caps <b>89</b><i>b </i>and <b>89</b><i>c </i>and performs suction recovery by the pumps.

A plurality of ejection openings are arranged on the ejection opening face of the printing head. Among the various ink-jet printing apparatuses, some of the ink-jet printing apparatuses have ejection openings that are not uniform size and rather differentiate per row of ejection openings to permit printing of an image at higher resolution. When a plurality of kinds of ejection openings of different shapes are present, the conventional ink-jet printing apparatus is provided with the caps in a number corresponding to shapes and kinds of the ejection openings, which requires a large space and hinders down-sizing of the overall apparatus. On the other hand, when an attempt is made to perform suction recovery for all the ejection openings with one cap, fluctuations in suction may result due to differences of flow resistance of the ink caused by the shape of the ejection openings.

More particularly, the row of the ejection openings having high flow resistance lacks ink suction force if the same suction force is applied in comparison with the row of the ejection openings having low flow resistance upon cap suction to make it impossible to effectively perform suction recovery. In order to perform suction for the row of the ejection openings having high flow resistance, a long period of suction operation is required, or the ink of increased viscosity plugging the ejection openings cannot be suctioned satisfactorily. On the other hand, from the row of the ejection openings having low flow resistance is suctioned an unnecessarily large amount of ink if the same suction process as that for the ejection openings having high flow resistance is performed, resulting in a waste of ink. Furthermore, excessive suction may cause retention of bubbles within the ejection opening to possibly make normal ink ejection impossible.

SUMMARY OF THE INVENTION

The present invention has been achieved for solving the problems in the prior art. Therefore, the present invention can provide an ink-jet printing apparatus and a recovery processing method of an ejection port which can satisfactorily perform a recovery process for respective ejection openings having different ink flow resistances and permit down-sizing.

According to one aspect of the present invention, an ink-jet printing apparatus including a printing head having a plurality of ejection openings and a cap covering the ejection opening face where a plurality of ejection openings of the printing head is arranged, and suction means suctioning ink from the ejection openings covered by the cap, comprises a sealing member being provided within the cap for sealing a portion of the plurality of ejection openings. In the ink-jet printing apparatus, when the of the plurality of ejection openings are sealed by the sealing member, an operation for suctioning ink from the ejection openings which are not sealed is performed by the suction means.

According to another aspect of the present invention, an ink-jet printing apparatus has a cap for covering an ejection opening face of a printing head in which a plurality of ejection openings are arranged, wherein the cap comprises a projecting lip portion surrounding a plurality of ejection openings when the cap covers the ejection opening face and a projecting portion formed inside surrounded by the lip portion and sealing a portion of the plurality of ejection openings, and wherein when the lip portion contacts with the ejection opening face at a predetermined position, the projecting portion seals the portion of ejection openings, and when the cap moves in a direction parallel to the ejection opening face to contact the ejection opening face at a position different from the predetermined position, the projecting portion does not seal the portion of ejection openings.

According to another aspect of the present invention, an ink-jet printing apparatus has a cap for covering an ejection opening face of a printing head in which a plurality of ejection openings are arranged, wherein the cap comprises a projecting lip portion surrounding a plurality of ejection openings when the cap covers the ejection opening face, a deformable lip portion formed at the projecting tip end of the lip portion, and a projecting portion formed inside surrounded by the lip portion and sealing a portion of the plurality of ejection openings, and wherein when the lip portion is applied with a predetermined contact force at a predetermined position to contact with the ejection opening face, the deformable lip portion is deformed and the projecting portion seals the portion of ejection openings, and when the lip portion is applied with a force less than the predetermined contact force at the predetermined position to contact with the ejection opening face, the deformable lip portion is not deformed and the projecting portion does not seal the portion of ejection openings.

According another aspect of the present invention, an ink-jet printing apparatus has a cap for covering an ejection opening face of an ink head in which a plurality of ejection openings are arranged, wherein the cap comprises a projecting lip portion surrounding a plurality of ejection openings when the cap covers the ejection opening face, a projecting portion formed inside surrounded by the lip portion and sealing a portion of the plurality of ejection openings, and a projecting portion actuating portion for moving the projecting portion for sealing the portion of ejection openings when a suction process of the ejection openings other than the portion of ejection openings is performed, and for moving the projecting portion for releasing the seal of the portion of ejection openings while the suction process of the portion of ejection openings is performed.

According to another aspect of the present invention, an ejection recovery processing method of an ejection port comprises a covering step of covering by a cap an ejection opening face on which is arranged a plurality of ejection openings, a sealing step of sealing a portion of the plurality of ejection openings by a sealing member provided within the cap, and a suction step of suctioning the ink from ejection openings not sealed by the sealing member in the sealing step.

By employing the above structure, upon covering the ejection opening face with the cap at the predetermined position, the projecting portion is contacted with the predetermined row of the ejection openings, such as the ejection openings having low flow resistance, to seal the predetermined row of the ejection openings. By performing suction in this condition, ink is suctioned from the row of the ejection openings other than the predetermined row of ejection openings. Then, after sufficiently suctioning the ink from the row of ejection openings other than the predetermined row of ejection openings, the cap is moved to release sealing by the projecting portion to effect suctioning. Then, ink is suctioned from the predetermined row of ejection openings. Thus, ink can be suctioned from all of the ejection openings in just proportion.

The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an ink-jet printing apparatus;

FIG. 2 is a perspective view of a printing head and an ink tank;

FIG. 3 is a diagrammatic illustration showing an ejection opening face;

FIG. 4 is a perspective view of a cap;

FIGS. 5A to <b>5</b>C are sections showing a state of contact between the cap and the ejection opening face, in which

FIG. 5A shows a non-contacting condition, FIG. 5B shows a first recovery stage and FIG. 5C denotes a second recovery stage;

FIGS. 6A to <b>6</b>C are sections showing a state of contact between another embodiment of the cap and the ejection opening face, in which FIG. 6A shows a non-contacting condition, FIG. 6B shows a first recovery stage and FIG. 6C denotes a second recovery stage;

FIGS. 7A and 7B are sections showing a state of contact between another embodiment of the cap and the ejection opening face, in which FIG. 7A shows first recovery stage and FIG. 7B denotes a second recovery stage; and

FIGS. 8A and 8B are sections showing the conventional printing head portion and a recovery unit portion, in which FIG. 8A shows the printing head portion and FIG. 8B shows the recovery unit portion.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the present invention will be discussed hereinafter with reference to the drawings.

FIG. 1 is a perspective view of one embodiment of an ink-jet printing apparatus according to the present invention.

The ink-jet printing apparatus <b>1</b> has a carriage <b>2</b>. On the carriage <b>2</b>, a printing head (not shown), a black ink tank <b>4</b> storing a black ink, and a color ink tank <b>5</b> storing cyan, magenta and yellow inks are provided. The carriage <b>2</b> is fixed on a frame <b>6</b> at both end portions for movement along a guide shaft <b>7</b> and a guide rail <b>8</b> disposed in parallel to the frame <b>6</b>. The carriage <b>2</b> is moved by a driving force of a carriage motor (not shown) transferred through a carriage belt (not shown). The carriage motor can be a stepping motor or the like.

On the other hand, a printing medium P stacked on an automatic sheet feeder <b>10</b> or upper cassette <b>11</b> and lower cassette <b>12</b> is fed by a paper feeding mechanism (not shown) and is fed to a predetermined print start position as pinched by the feeding roller <b>9</b> and a pinch roller (not shown). Then, the carriage <b>2</b> performs scanning. During scanning by the carriage <b>2</b>, the printing head performs printing. When one path of scan is completed, the printing medium is fed for a predetermined amount in a direction perpendicular to the scanning direction of the carriage <b>2</b>. By repeating the printing operation and feeding operation, printing over the entire printing medium can be performed.

On the other hand, the ink-jet printing apparatus <b>1</b> performs a recovery operation by a recovery mechanism <b>14</b> during standby of a command of printing or before and after the printing operation or at an appropriate timing during printing in order to recover performance or maintain good condition of the printing head. In the recovery mechanism, a cap, a suction pump, a wiping member and so on are provided. The construction and operation of the recovery mechanism will be explained later.

FIG. 2 is a perspective view of the printing head and the ink tank.

The printing head <b>3</b> is provided with ejection opening face <b>20</b> on the surface opposing the printing medium as loaded on the carriage, and is provided with rows of plural ejection openings <b>27</b><i>b </i>and <b>27</b><i>c </i>arranged on the ejection opening face. Each election opening is applied with an electrical signal necessary for ink ejection by an electrical circuit board <b>25</b>. The electrical circuit board <b>25</b> contacts a predetermined position in a holder of the carriage when the printing head <b>3</b> is loaded on the carriage. The electrical signal is received from the contact point.

On the other hand, the black ink tank <b>4</b> and the color ink tank <b>5</b> are detachably loaded in a head holder <b>28</b>. The ink of the black ink tank <b>4</b> is filled in each ejection opening of the row of the ejection openings <b>27</b><i>b </i>via an ink supply passage (not shown). Similarly, each ink of cyan, magenta, and yellow of the color ink tank <b>5</b> is also filled in each ejection opening of the row of ejection openings <b>27</b><i>c </i>via the ink supply passage.

FIG. 3 is a diagrammatic illustration showing the ejection opening face.

In the row of the ejection openings <b>27</b><i>b </i>ejecting the black ink, n in number of ejection openings <b>30</b><i>b</i><b>1</b>, <b>30</b><i>b</i><b>2</b>, . . . <b>30</b><i>bn </i>are arranged in alignment. The size of each ejection opening <b>30</b> is 22 μm×22 μm. From each ejection opening <b>30</b>, an ink passage (not shown) is extended. Each ink passage is communicated with an ink chamber (not shown). The ink of the black ink tank is filled up to each ejection opening via the ink chamber from the ink supply passage. Furthermore, in each ink passage, a heater <b>20</b><i>a </i>is provided corresponding to each ejection opening <b>30</b>. In FIG. 3, only the heater corresponding to ejection opening <b>30</b><i>b</i><b>1</b> is illustrated. In order to eject the ink, the heater is heated to generate a bubble in the ink. Then, by generation of pressure from the bubble, a predetermined amount of ink in the form of a droplet is ejected. In the shown embodiment, the heater size is 26'32 μm²and the ejection amount is 8×10⁻¹⁵m³(8 pl).

The row of the ejection openings <b>27</b><i>c </i>ejecting respective colors of color inks is divided per n in number for each ink color. Ejection openings <b>31</b><i>y</i><b>1</b> . . . <b>31</b><i>yn </i>for ejecting the yellow ink, the ejection openings <b>31</b><i>m</i><b>1</b> . . . <b>31</b><i>mn </i>for ejecting the magenta ink and the ejection openings <b>31</b><i>c</i><b>1</b> . . . <b>31</b><i>cn </i>for ejecting the cyan ink are arranged in alignment. The ejection opening <b>31</b> of the row of the ejection openings <b>27</b><i>c </i>has the same construction as the ejection opening <b>30</b>. The size of the ejection opening <b>31</b> is smaller than that of the ejection opening <b>30</b> and is 17×17 μm². The size of the corresponding heater is 24×26 μm², and ejection amount is 4×10⁻¹⁵m³(4 pl). rows of the ejection openings in the shown embodiment is 42.3 μm to enable pixel formation corresponding to 600 dpi of printing density. The arrangement pitch may be appropriately determined for desired image formation. Although two rows of the ejection openings are formed in the shown embodiment, it is also possible to arrange a greater number of rows of ejection openings. For example, four rows of ejection openings may be formed for each color of cyan, magenta, yellow and black.

Since sizes of the ejection openings differ in the row of ejection openings <b>27</b><i>b </i>and the row of ejection openings <b>27</b><i>c</i>, flow resistances in the ejection openings are also different. To satisfactorily perform ink suction for the respective kinds of rows of ejection openings with different flow resistances without wasting the ink, the shown embodiment of the recovery mechanism has the following construction.

FIG. 4 is a perspective view of the cap.

The cap <b>40</b> comprises a lip portion <b>41</b> projecting from the periphery of a base portion <b>49</b>. Upon contacting the cap <b>40</b> onto the ejection opening face <b>20</b>, the lip portion <b>41</b> abuts onto the ejection opening face <b>20</b>. Upon abutting, rows of the ejection openings <b>27</b><i>b </i>and <b>27</b><i>c </i>are surrounded by the lip portion <b>41</b>.

Within the lip portion <b>41</b>, ink suction opening <b>45</b> is provided. The ink suction opening <b>45</b> is communicated with a suction pump (not shown). When the suction pump is driven, dust and dirt deposited on the ejection opening or ink having increased viscosity are suctioned through the ink suction opening <b>45</b>.

Furthermore, adjacent the ink suction opening, projecting portion <b>48</b> is provided along the longitudinal direction of the lip portion <b>41</b>. A height of the projecting portion <b>48</b> is substantially the same height as the circumferential lip portion <b>41</b>.

As the material of the cap <b>40</b>, an elastic material, such as rubber or the like for effectively providing gas tightness upon abutting the lip portion <b>41</b> onto the ejection opening face <b>20</b>, is used. Furthermore, in the light of wettability of the ink, chlorinated butyl rubber, silicone rubber and like are preferred. It is preferred that the material of the projecting portion <b>48</b> is the same as the material of the cap <b>40</b>.

FIGS. 5A to <b>5</b>C are sections showing states of abutment between the cap and the ejection opening face.

Upon initiation of the recovery process, the carriage is moved so that the printing head is positioned in opposition to the cap. When the printing head reaches the position opposing to the cap, the cap <b>40</b> is moved upward as shown in FIG. 5A to abut onto the ejection opening face <b>20</b> of the printing head. It should be noted that the printing head is placed at a position where both of the rows of the ejection openings <b>27</b><i>b </i>and <b>27</b><i>c </i>are surrounded by the lip portion <b>41</b>.

When the cap <b>40</b> is moved upward and the lip portion <b>41</b> abuts onto the ejection opening face <b>20</b> of the printing head, the projecting portion <b>48</b> having the same height as the lip portion <b>41</b>, as shown in FIG. 5B, contacts with the ejection openings <b>30</b> to seal the ejection openings <b>30</b>.

Since each ejection opening <b>30</b> has a greater opening area than that of each ejection opening <b>31</b>, each ejection opening <b>30</b> has a smaller flow resistance than the ejection opening <b>31</b> upon suction of the ink. Therefore, if the pump is driven in a condition in which ejection openings <b>30</b> and ejection openings <b>31</b> are open without sealing the ejection openings <b>30</b> with the projecting portion <b>48</b>, ink is mainly suctioned from the ejection openings <b>30</b> having smaller flow resistance, and suctioning ink from the ejection openings <b>31</b> is difficult. However, when suction is performed after sealing the ejection openings <b>30</b> having low flow resistance, the ink is suctioned from the ejection openings <b>31</b> and ink is not suctioned from the ejection openings <b>30</b>. In the shown embodiment, the suction operation in the condition shown in FIG. 5B is referred to as the first recovery stage. In the first recovery stage, the ejection openings having small flow resistance and large ejection amount are selectively sealed to allow the suction process for the remaining ejection openings that are not sealed.

When the suction process of the ejection openings <b>31</b> is satisfactorily performed, the cap <b>40</b> is moved downwardly away from the printing head and is laterally moved parallel to the arrangement direction of the rows of the ejection openings <b>27</b><i>b </i>and <b>27</b><i>c </i>by a predetermined amount (direction shown by the arrow in FIG. <b>5</b>C). Then, the cap <b>40</b> is again moved upward to contact with the ejection opening face <b>20</b>. At this time, as shown in FIG. 5C, the projecting portion <b>48</b> contacts at a position not to seal the ejection openings <b>30</b>. Namely, the cap <b>40</b> is abutted in the condition where all of the ejection openings <b>30</b> and <b>31</b> are sealed. By performing suction by driving the suction pump in this condition, ink is mainly suctioned from the ejection openings <b>30</b> that were sealed in the first recovery stage. This is referred to as the second recovery stage.

As set forth above, by performing suction while sealing the ejection openings <b>30</b> having low flow resistance in the first recovery stage, and by performing suction after removing the seal of the ejection openings <b>30</b> in the second recovery stage, ink suction in just proportion can be performed for respective ejection openings. Namely, with one cap, suction for a plurality of kinds of ejection openings can be performed in just proportion.

In the shown embodiment, after completion of the first recovery stage and in transition to the second recovery stage, the cap <b>40</b> is moved down and moved laterally for the predetermined amount in the direction shown by the horizontal arrow, and then is moved upward again to contact with the ejection opening face <b>20</b> to place the projecting portion <b>48</b> out of contact with the ejection openings <b>30</b>. However, it is also possible that, after lowering the cap <b>40</b>, the printing head is moved by the predetermined amount in a lateral direction opposite to the direction of the horizontal arrow and stopped, and then the cap <b>40</b> is elevated to contact with the printing head.

Second Embodiment

In the shown embodiment, explanation will be given for the structure of the lip portion of the cap different from the first embodiment.

FIGS. 6A to <b>6</b>C are sections showing the cap and the printing head ejection opening face.

As shown in FIG. 6A, the shown embodiment of the cap <b>40</b> is further provided with projection <b>46</b> at the tip end of the lip portion <b>41</b>. The projection <b>46</b> is located at a position higher than the projecting portion <b>48</b>. The projection <b>46</b> is formed with a material softer than the lip member <b>41</b> that is formed with an elastic material.

Similar to the first embodiment, when the recovery process is initiated, the carriage is moved to the position where the printing head opposes the cap. When the printing head reaches the position opposing the cap, the cap <b>40</b> is elevated to contact with the ejection opening face <b>20</b> of the printing head. Contacting is performed at the position where the lip portion <b>41</b> surrounds all of the ejection openings <b>30</b> and <b>31</b>.

Then, at the first recovery stage, the projection <b>46</b> provided at the tip end of the lip portion <b>41</b> contacts the ejection opening face <b>20</b>. Even after contacting the projection <b>46</b> onto the ejection opening face <b>20</b>, the cap <b>40</b> is further elevated. As shown in FIG. 6B, by further upward movement of the cap <b>40</b>, the projection <b>46</b> is collapsed by elastic deformation to be bent toward the lip portion <b>41</b>. When the projection <b>46</b> is collapsed, the projecting portion <b>48</b> contacts with the ejection opening face <b>20</b> to seal the ejection openings <b>30</b>. By operating the suction pump in this condition, the ink is suctiioned from the ejection openings <b>31</b> which are not sealed.

After completion of the suction operation in the first recovery stage, the cap <b>40</b> is lowered by a predetermined amount. The magnitude of lowering of the cap <b>40</b> is to the extent to slightly weaken the contact force with the ejection opening face <b>20</b>. Furthermore, as shown in FIG. 6C, the collapsed projection <b>46</b> is restored to its original shape still in contact with the ejection opening face <b>20</b>. Furthermore, by lowering the cap <b>40</b>, the projecting portion <b>48</b> that had sealed the ejection openings <b>30</b> is released from the ejection openings <b>30</b>. Since the projection <b>46</b> is located at higher position than the projecting portion <b>48</b>, a gap is formed between the projecting portion <b>48</b> and the ejection openings <b>30</b>. In this condition, when the suction pump is driven, the ink is mainly suctioned from the ejection openings <b>30</b> having low flow resistance. It should be noted that the position where the cap <b>40</b> is lowered and stopped is where the projection <b>46</b> is still in contact with the ejection opening face <b>20</b> without collapsing to maintain the inside of the lip portion <b>40</b> in an airtight condition.

Thus, by providing the projection <b>46</b> having different elastic characteristics at the tip end of the lip portion <b>41</b> and deforming the projection <b>46</b>, ink suction can be performed for a plurality of ejection openings having different flow resistances in just proportion without moving the cap in left and right (lateral) directions. Accordingly, since the cap is not required to move in the direction perpendicular to the arrangement direction of the ejection openings, this embodiment is applicable for an apparatus having no space for such movement. In addition, the drive mechanism can be simplified.

Third Embodiment

FIGS. 7A and 7B are sections of the shown third embodiment of the cap.

The lip portion <b>41</b> of the shown embodiment of the cap <b>40</b> is similar to that of the first embodiment. However, as shown in FIG. 7A, a projecting portion <b>70</b> is not fixed to the base portion <b>49</b> as in the first and second embodiments. Similarly to the first embodiment, the shape of the projecting portion <b>70</b> is a rectangular parallelepiped shape elongated in the longitudinal direction of the cap <b>40</b> along the rows of the ejection openings. At several portions of the projecting portion <b>70</b> on the surface opposing the ejection opening face, support stems <b>71</b> are formed integrally. The support stems <b>71</b> extend toward the base portion <b>49</b> and are inserted into the support holes <b>72</b>. Furthermore, on a part of each support stem or shaft <b>71</b>, a ring shaped stopper <b>74</b> is provided. On the other hand, in a part of each support hole <b>72</b>, a recess <b>73</b> is provided surrounding the support hole <b>72</b>.

It should be noted that other portions of the cap <b>40</b>, such as ink suction opening <b>45</b>, the base portion <b>49</b> and so on are the same as those in the first embodiment. In addition, the ejection openings <b>30</b> formed on the ejection opening face <b>20</b> have low flow resistance in comparison with the ejection openings <b>31</b>.

Similarly to the first embodiment, when the recovery process is initiated, at first, the carriage is moved to a position where the printing head opposes the cap. Then, when the printing head reaches the position opposing the cap, the cap <b>40</b> is elevated to contact the ejection opening face <b>20</b> of the printing head. Contact is performed such that the lip portion <b>41</b> surrounds all of the ejection openings <b>30</b> and <b>31</b>.

Then, by not shown driving means, the projecting portion <b>70</b> is moved upward to seal the ejection openings <b>30</b> (see FIG. <b>7</b>A). At this time, stopper <b>74</b> penetrates into the recess <b>73</b>. This condition is the first recovery stage. Then, similarly to the first embodiment, the suction pump is driven to perform suction from the ejection openings <b>31</b>. At this time, with the projection portion <b>70</b>, the ejection openings <b>30</b> are completely sealed. Also, since the stopper <b>74</b> enters into the recess <b>73</b>, an airtight sealing of the gap between the support stem <b>71</b> and the support hole <b>72</b> is accomplished. By this, the suction force of the suction pump effectively acts on the ejection openings <b>31</b>.

It should be noted that the driving means of the projecting portion <b>70</b> uses, for example, the carriage motor in the ink-jet printing apparatus <b>1</b> as its driving source, and can include a cam mechanism driven via a gear. The driving means of the projecting portion <b>70</b> may also be formed with an actuator performing reciprocal linear motion, such as plunger type solenoid.

When the suction process from the ejection openings <b>31</b> is completed, the projecting portion <b>70</b> is lowered by the not shown driving means to release the seal of the ejection openings (see FIG. <b>7</b>B). This condition is the second recovery stage. Then, similarly as in the first embodiment, the suction pump is driven to suction the ink mainly from the ejection openings <b>30</b> having low flow resistance.

Thus, by providing the vertically movable projecting portion <b>70</b> within the cap <b>40</b>, the lip portion <b>41</b> of the cap <b>40</b> contacts with the ejection opening face <b>20</b>. Thereafter, the cap <b>40</b> per se does not move further to seal the ejection openings having low flow resistance or to release sealing. Accordingly, even in a structure having small space for moving the cap, the recovery process of respective ejection openings can be performed effectively in just proportion.

Other Features

Incidentally, the present invention achieves distinct effects when applied to a print head or a printing apparatus which has means for generating thermal energy, such as electrothermal transducers or lasers, and which causes changes in ink by the thermal energy so as to eject ink. This is because such a system can achieve high density and high resolution printing.

A typical structure and operational principle thereof are disclosed in U.S. Pat. Nos. 4,723,129 and 4,740,796, and it is preferable to use this basic principle to implement such a system. Although this system can be applied either to on-demand type or continuous type inkjet printing systems, it is particularly suitable for the on-demand type apparatus. This is because the on-demand type apparatus has electrothermal transducers, each disposed on a sheet or liquid passage that retains liquid (ink), and operates as follows: first, one or more drive signals are applied to the electrothermal transducers to generate thermal energy corresponding to printing information; second, the thermal energy induces sudden temperature rise that exceeds the nucleate boiling so as to cause the film boiling on heating portions of the print head; and third, bubbles are grown in the liquid (ink) corresponding to the drive signals. By using the growth and collapse of the bubbles, the ink is expelled from at least one of the ink ejection orifices of the head to form one or more ink drops. The drive signal in the form of a pulse is preferable because the growth and collapse of the bubbles can be achieved instantaneously and suitably by this form of drive signal. As a drive signal in the form of a pulse, those described in U.S. Pat. Nos. 4,463,359 and 4,345,262 are preferable. In addition, it is preferable that the rate of temperature rise of the heating portions described in U.S. Pat. No. 4,313,124 be adopted to achieve better printing.

U.S. Pat. Nos. 4,558,333 and 4,459,600 disclose the following structure of a print head, which is incorporated into the present invention: this structure includes heating portions disposed on bent portions in addition to a combination of the ejection orifices, liquid passages and the electrothermal transducers disclosed in the above patents. Moreover, the present invention can be applied to structures disclosed in Japanese Patent Application Laid-Open Nos. 59-123670 (1984) and 59-138461 (1984) in order to achieve similar effects. The former discloses a structure in which a slit common to all the electrothermal transducers is used as a common ejection orifice of the electrothermal transducers, and the latter discloses a structure in which openings for absorbing pressure waves caused by thermal energy are formed corresponding to the ejection orifices. Thus, irrespective of the type of the print head, the present invention can achieve printing positively and effectively.

The present invention can be also applied to a so-called full-line type print head whose length equals the maximum length across a printing medium. Such a print head may consist of a plurality of print heads combined together, or one integrally arranged print head.

In addition, the present invention can be applied to various serial type print heads: a print head fixed to the main assembly of a printing apparatus; a conveniently replaceable chip type print head which, when loaded on the main assembly of a printing apparatus, is electrically connected to the main assembly, and is supplied with ink therefrom; and a cartridge type print head integrally including an ink reservoir.

It is further preferable to add a recovery system, or a preliminary auxiliary system for a print head as a constituent of the printing apparatus because they serve to make the effects of the present invention more reliable. Examples of the recovery system are a capping means and a cleaning means for the print head, and a pressure or suction means for the print head. Examples of the preliminary auxiliary system are a preliminary heating means utilizing electrothermal transducers or a combination of other heater elements and the electrothermal transducers, and means for carrying out preliminary ejection of ink independently of the ejection for printing. These systems are effective for reliable printing.

The number and type of print heads to be mounted on a printing apparatus can be also changed. For example, only one print head corresponding to a single color ink, or a plurality of print heads corresponding to a plurality of inks different in color or concentration can be used. In other words, the present invention can be effectively applied to an apparatus having at least one of the monochromatic, multi-color and full-color modes. Here, the monochromatic mode performs printing by using only one major color such as black. The multi-color mode carries out printing by using different color inks, and the full-color mode performs printing by color mixing.

Furthermore, although the above-described embodiments use liquid ink, inks that become liquid when the printing signal is applied can be used: for example, inks can be employed that solidify at a temperature lower than room temperature and are softened or liquefied at room temperature. This is because in the inkjet system, the ink is generally temperature adjusted in a range of 30° C.-70° C. so that the viscosity of the ink is maintained at such a value that the ink can be ejected reliably.

In addition, the present invention can be applied to such apparatus where the ink is liquefied just before the ejection by the thermal energy as follows so that the ink is expelled from the orifices in the liquid state, and then begins to solidify on hitting the printing medium, thereby preventing the ink evaporation: the ink is transformed from solid to liquid state by positively utilizing the thermal energy which would otherwise cause a temperature rise; or the ink, which is dry when left in air, is liquefied in response to the thermal energy of the printing signal. In such cases, the ink may be retained in recesses or through-holes formed in a porous sheet as liquid or solid substances so that the ink faces the electrothermal transducers as described in Japanese Patent Application Laid-Open Nos. 54-56847 (1979) or 60-71260 (1985). The present invention is most effective when it uses the film boiling phenomenon to expel the ink.

Furthermore, the ink jet recording apparatus of the present invention can be employed not only as an image output terminal of an information processing device such as a computer, but also as an output device of a copying machine including a reader, and as an output device of a facsimile apparatus having a transmission and receiving function.

By employing the present invention, upon covering the ejection opening face with the cap at the predetermined position, the projecting portion is contacted with the predetermined row of the ejection openings, such as the ejection openings having low flow resistance, to seal the predetermined row of the ejection openings. By performing suction in this condition, ink is suctiioned from the row of the ejection openings other than the predetermined row of ejection openings. Then, after sufficiently suctioning the ink from the row of ejection openings other than the predetermined row of ejection openings, the cap is moved to release sealing by the projecting portion to effect suctioning. Then, ink is suctioned from the predetermined row of ejection openings. Thus, ink can be suctioned from all of the ejection openings in just proportion. Therefore, a satisfactory recovery process can be performed for all of the ejection openings having different flow resistances and a compact ink-jet printing apparatus and ejection recovery method can be provided.

Also, by further providing the modified lip portion to the lip portion of the cap, the seal by the projecting portion can be released by merely weakening the contact force to be exerted on the cap without moving the cap in parallel to the ejection opening surface after the first recovery stage is completed, so that it becomes applicable for the apparatus having no space to move the cap. Also, the cap drive mechanism can be simplified.

Also, by providing the mechanism for driving only the projecting portion, once the cap abuts on the ejection opening, the first recovery stage and the second recovery stage can be performed without moving the cap, thus achieving space saving.

The present invention has been described in detail with respect to preferred embodiments, and it will now be apparent from the foregoing to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and it is the intention, therefore, that the appended claims cover all such changes and modifications as fall within the true spirit of the invention.